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  Java Practices -> Serve binary content
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<div class='page-title'>Serve binary content</div>

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<br>Servlets usually serve some form of text - HTML, XML, plain text, and so on.
Servlets can also serve binary content, such as images or .pdf files.

<P>Here is an example of a simple servlet that serves binary content.
It serves a .pdf file of a fixed name, located in the web application's root directory.
<br>
<PRE>

<span class='keyword'>import</span> java.io.*;

<span class='keyword'>import</span> javax.servlet.ServletException;
<span class='keyword'>import</span> javax.servlet.ServletOutputStream;
<span class='keyword'>import</span> javax.servlet.http.HttpServlet;
<span class='keyword'>import</span> javax.servlet.http.HttpServletRequest;
<span class='keyword'>import</span> javax.servlet.http.HttpServletResponse;

<span class='comment'>/**
 Servlet that serves binary data, not text.
  
 &lt;P&gt;This servlet serves a static .pdf file, but the idea is the same with other 
 forms of data.
*/</span>
<span class='keyword'>public</span> <span class='keyword'>class</span> ServeBinary <span class='keyword'>extends</span> HttpServlet {

  <span class='keyword'>@Override</span> <span class='keyword'>protected</span> <span class='keyword'>void</span> doGet(
    HttpServletRequest aRequest, HttpServletResponse aResponse
  ) <span class='keyword'>throws</span> ServletException, IOException {
    serveBinary(aRequest, aResponse);
  }
   
  <span class='keyword'>@Override</span> <span class='keyword'>protected</span> <span class='keyword'>void</span> doPost(
    HttpServletRequest aRequest, HttpServletResponse aResponse
  ) <span class='keyword'>throws</span> ServletException, IOException {
    serveBinary(aRequest, aResponse);
  }
  
  <span class='comment'>// PRIVATE //
</span>  
  <span class='keyword'>private</span> <span class='keyword'>void</span> serveBinary(
    HttpServletRequest aRequest, HttpServletResponse aResponse
  ) <span class='keyword'>throws</span> IOException {
    log(<span class='literal'>"ServeBinary servlet."</span>);
   
    <span class='comment'>//IMPORTANT: set the MIME type of the response stream
</span>    aResponse.setContentType(<span class='literal'>"application/pdf"</span>);
    
    ServletOutputStream output = aResponse.getOutputStream();
    InputStream input =  <span class='keyword'>null</span>;
    <span class='keyword'>try</span> { 
      <span class='comment'>//serve a fixed file, located in the root folder of this web app 
</span>      input =  getServletContext().getResourceAsStream(<span class='literal'>"test.pdf"</span>);
      <span class='comment'>//if raw bytes are already available, use this instead :
</span>      <span class='comment'>//InputStream inputBytes = new ByteArrayInputStream(myBytes);
</span>      
      <span class='comment'>//transfer input stream to output stream, via a buffer
</span>      <span class='keyword'>byte</span>[] buffer = <span class='keyword'>new</span> <span class='keyword'>byte</span>[<span class='literal'>2048</span>];
      <span class='keyword'>int</span> bytesRead;    
      <span class='keyword'>while</span> ((bytesRead = input.read(buffer)) != -<span class='literal'>1</span>) {
         output.write(buffer, <span class='literal'>0</span>, bytesRead);
      }
    }
    <span class='keyword'>finally</span> {
      <span class='comment'>//close all streams
</span>      output.close();
      <span class='keyword'>if</span> (input != <span class='keyword'>null</span>) input.close();
    }
    
    log(<span class='literal'>"Done."</span>);
  }
}
 
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